electric heat

Question 1

An example of a resistive load is a:

Answer 1

crankcase heater

Question 2

A GFCI circuit breaker:

Answer 2

Detects impedance at appliances.

Question 3

Voltage imbalance between any legs of a 3-phase power supply may not exceed:

Answer 3

2%

Question 4

The limit switch on an electric furnace is a:

Answer 4

automatic reset switch

Question 5

The sequencer timers on electric heaters will usually energize the 1st heating element after a time delay of:

Answer 5

1-30 seconds.

Question 6

The amount of BTU produced per one watt is:

Answer 6

3,413 BTU

Question 7

60 amps and 230 volts, what is the power?

Answer 7

13800 watts

Question 8

A furnace is using 15,500 watts of power, what is that in kW?

Answer 8

15.5 kW

Question 9

Sequence timers use ________ to close the contact points to the heater element.

Answer 9

heated-snap discs or heated bi metal rings

Question 10

An electric furnace heating thermostat must:

Answer 10

Open on a rise close on a drop.

Question 11

Standard thermostat heat anticipator is _______ and wired in _________ with the heating control.

Answer 11

adjustable/ series

Question 12

Some thermostat manufacturers require a jumper connection on the thermostat sub-base of heating and cooling thermostats in order to:

Answer 12

use a single transformer.

Question 13

Most electric heat elements use the following safeties to prevent overheating.

Answer 13

Snap-disc and fusible link.

Question 14

70 amps and 230 volts, what is the BTUs?

Answer 14

Find wattage P=IV 16,100 x 3.413 = 54,949

Question 15

The control that prevents duct heaters from operating unless there is adequate supply air is:

Answer 15

fan interlock.

Question 16

The coefficient of performance for electric resistance is:

Answer 16

1 to 1

Question 17

What is the maximum kW element used on each contact of a residential heat sequencer?

Answer 17

5 kW

Question 18

Electric heaters are generally rated at _______ volts AC for kW output.

Answer 18

240

Question 19

An automatic reset safety switch in a heating element generally opens at _______ F

Answer 19

130-190

Question 20

The first stage of a sequence timer usually has a set of contacts to:

Answer 20

start the blower fan motor.

Question 21

Most heating elements are mounted on which type of insulators?

Answer 21

Mica or ceramic

Question 22

What will a 10 kW heater wired to 480 volts draw in amps?

Answer 22

21 amps

Question 23

The purpose of a sequencer is to:

Answer 23

avoid a sudden power overload.

Question 24

Two major factors in determining the temperature rise of an electric furnace are:

Answer 24

Furnace kW and CFM

Question 25

A major cause of electrical heat element burnout is:

Answer 25

low airflow.

Question 26

A technician is checking resistance on a delta three phase motor. If one element is open, he would read:

Answer 26

He would read that between L1- L2-L3 there is ONE reading of infinity ohm.s.

Question 27

The purpose of setting a heat sequencer anticipator properly is:

Answer 27

control cycling time.

Question 28

10 kw heater installed in a 2 ton system should have a flow of _____ CFM

Answer 28

300-500

Question 29

Resistance to air flow (static pressure) is measured in an electric heater in:

Answer 29

inches of water column

Question 30

To properly set a heat anticipator, the technician should measure amps between terminals _________ on thermostat sub-base.

Answer 30

R-W

Question 31

If a technician installs a 15 kW electric furnace on a 3 ton system, there should be how many thermostat conductors?

Answer 31

5. R,B,W,Y,G

Question 32

To measure grill air speed, the tech should use a:

Answer 32

anemometer.

Question 33

a 1/3 single phase PSC electric blower would draw approx. _________ at 240 volts AC

Answer 33

2-4 Amps

Question 34

On a delta phase motor L1- L2 11 ohms L1 - L3 22 ohms L2 - L3 11 ohms whats wrong?

Answer 34

L1 -L3 is shorted

Question 35

a 1200 CFM furnace operating with a 10 kW heater at 240 volt AC would have a temperature rise of _____________ F

Answer 35

20-30

Question 36

In a heat pump, the heating element is controlled by what stage of the thermostat?

Answer 36

Auxiliary heating.

Question 37

Typical RPM of a residential direct driven blower is:

Answer 37

1,000 - 1,200 RPM

Question 38

The drive belt width used on fractional HP motors is:

Answer 38

A

Question 39

Most residential air conditioning and electric heating systems will have a fan system rated for a maximum total pressure loss of:

Answer 39

0.02 - 0.1 inches of WC

Question 40

Turning vanes are added to the sheet metal elbows to:

Answer 40

increase air velocity.

Question 41

The MAX recommended return air velocity of a residential filter grill is:

Answer 41

400 fpm